The present invention is related to a pressure regulation apparatus for an ink reservoir, and more particularly, to a pressure regulation apparatus for an ink reservoir, which applies an elastic bag and a porous filter for complementarily regulating the back pressure within the ink reservoir to reach a steady balance of a pressure difference within and outside the ink reservoir.
Nowadays, the ink-jet printer has become a necessary accessory printing equipment of a computer in modern information time. Typically, there are two mechanisms for ejecting drops of the ink from the ink reservoir. One is the piezoelectric pressure wave type, and the other is the thermal bubble type. No matter which type is used, the pressure must be controlled from the interior of the ink reservoir so that the ink reservoir of an ink-jet printer is under the best usage without ink leakage or ink blockage. That is, the back pressure (which means the partial vacuum within the ink reservoir or the pressure within the ink reservoir is slightly smaller than the atmospheric pressure) within the interior of the ink reservoir has to be maintained at a proper and steady condition. Generally, the ink reservoir of the ink-jet printer can be divided into two types. One is the ink reservoir for holding the ink only, and the other is the ink reservoir with a printing chip. The former must be co-operated with a print head mounted in the ink-jet printer, which has a printing chip. The latter combines the ink reservoir and the printing chip together, which is called inkjet head (ink-jet pen). Nevertheless, it is to be understood that the description below is limited to neither of the two above types. On the contrary, it is intended to cover a pressure regulation apparatus for an ink reservoir, which can be used in every kind of ink reservoir when the pressure needs to be regulated.
U.S. Pat. No. 5,409,134 disclosed a pressure-sensitive accumulator for an ink-jet pen, as shown in FIG. 1. The accumulator includes an expandable bag 11 which is mounted attachably to a spring 12. The upwardly projecting boss 131 is mounted on the cap 13 of the ink reservoir 1 so that the interior of the bag 11 is in communication with the ambient air outside the ink reservoir 1 through the central duct 132 which passes through the projecting boss 131. When the ink reservoir 1 is used for printing, the space of air increases (and hence, the back pressure increases) as the ink is consumed. The bag 11 expands as a result of the back pressure increase. Expansion of the bag 11 deflects the spring 12. The spring 12 bent originally will tend to be straight and accumulate the recovery strength. Meanwhile, the ambient air outside the ink reservoir 1 enters the interior of the bag 11 through the projecting boss 131 so that the back pressure within the ink reservoir 1 and the outside ambient pressure reach a proper balance. Similarly, if some factors result in the ambient pressure outside the ink reservoir 1 smaller than the pressure within the ink reservoir 1, the recovery strength of the spring 12 will make itself back to its original bent shape. The recovery strength of the spring 12 tends to contract the bag 11. Therefore, the bag 12 volume decreases and the internal air within the ink reservoir 1 is squeezed out of the ink reservoir 1 so that the pressure within and outside the ink reservoir 1 can reach a balance.
In the operation of air regulation to maintain the pressure balance, a relative adjustment of the back pressure change within the ink reservoir 1 is accomplished by the relationship between the elasticity of the spring 12 and the expansion of the bag 11 mounted attachably thereto. Since the interior of the bag 11 has a big air capacity, the air capacity change generated by a bigger pressure difference is allowed. However, the spring 12 itself has a basic pressure requisite upon deformation, so it lacks the sensitivity of the pressure difference if the pressure difference is not big enough. On the other hand, in the respect of manufacturing technology, it is difficult to control the coefficient of elasticity of the spring 12 and the capacity change of the bag 11 accurately. It is easy to cause the spring 12 to be bent or relaxed while the pressure difference is just generated. However, the flexure and the deformation of the spring 12, which are caused by the pressure difference, will be slow down if the spring 12 has been bent to a certain extent. In addition, the spring 12 and the bag 11 might not have a good attachment, and we must consider the possible malfunction upon the assembly of the projecting boss 131. Therefore, the apparatus established according to this pressure regulation method might have a poor response to the pressure change after being used for a period of time. It might also cause a lower product pass rate when manufacturing.
Additionally, U.S. Pat. No. 5,526,030 disclosed another apparatus of the pressure regulation, as shown in FIG. 2. An opening 21 is mounted at the bottom of the ink reservoir 2. A sphere 22 is mounted concentrically within the opening 21. The sphere 22 is maintained within the opening 21 by a number of raised crush ribs 23 formed around the interior of the opening 21. The outside diameter of the sphere 22 is smaller than the inside diameter of the opening 21 to define an annular orifice 24 (as shown in FIG. 3). Under the opening 21, an inlet labyrinth 25 is provided, which is a path having a semicircular cross section between the hole 27 and the opening 21. The whole length of the inlet labyrinth 25 is sealed from both the ambient air and the reservoir by a cover 26. The proximal end of the inlet labyrinth 25 opens to the opening 21 and the distal end opens to the ambient air through a hole 27 mounted on the cover 26. When the pressure within the ink reservoir 2 is lower than that of the outside, the ambient air passes through the inlet labyrinth 25 and the annular orifice 24 to enter the ink reservoir 2 to balance the pressure within and outside the ink reservoir 2. When the pressure within the ink reservoir 2 is higher than that of the outside, the ink enters the inlet labyrinth 25 at the bottom of the ink reservoir 2 through the annular orifice 24 and is stored within the inlet labyrinth 25 temporarily. Nevertheless, when the pressure within the ink reservoir 2 returns to the normal, the ink stored within the inlet labyrinth 25 temporarily will reenter the ink reservoir 2 by the pressure difference and the capillarity.
This pressure regulation method is simpler than the former method which uses a bag and a spring. However, since the inlet labyrinth 25 at the bottom of the ink reservoir 2 can only keep a very small amount of ink, the inlet labyrinth 25 might not be able to completely keep the excessive ink if the pressure difference within and outside the ink reservoir 2 is too large. Therefore, the phenomenon of ink leakage, which means that the ink flows out from the ink reservoir 2 through the annular orifice 24, will happen. On the other hand, the annular orifice 24 formed by the relative cooperation between the raised crush ribs 23 and the opening 21 must have a good accuracy, or the capillarity can not proceed smoothly. Accordingly, the product pass rate is reduced.
In view of how important the pressure regulation is and its serious affect to the smoothly ejecting drops of ink from the ink reservoir, a pressure regulation apparatus for an ink reservoir is provided. The ink reservoir described in the present invention covers both the type of ink reservoir for only holding ink and the type of ink reservoir with a printing chip.
The main purpose of the present invention is to provide a pressure regulation apparatus for an ink reservoir, which applies the elastic bag and the porous filter for complementarily regulating the back pressure within the ink reservoir to obtain a steady and balanceable pressure difference within and outside the ink reservoir.
It is another object of the present invention to provide a pressure regulation apparatus for an ink reservoir, which includes the elastic bag and the porous filter for complementarily regulating the back pressure within the ink reservoir to obtain a steady and balanceable pressure difference within and outside the ink reservoir.
The characteristic of the present invention is that the pressure regulation apparatus for an ink reservoir uses both the elastic bag to respond immediately for a big pressure change and the porous filter to regulate sensitively for a slight pressure change. Therefore, the pressure difference within and outside the ink reservoir can be maintained within a steady range.
According to the present invention, a pressure regulation apparatus for an ink reservoir, comprises: an elastic bag mounted in the ink reservoir for freely passing an ambient air of an ambient environment outside the ink reservoir in and out the elastic bag, wherein the ink reservoir has an interior for holding an ink; and a porous filter mounted in the ink reservoir for entering the ambient air outside the ink reservoir into the interior of the ink reservoir therethrough, thereby the elastic bag and the porous filter complementarily regulating a pressure difference between the interior of the ink reservoir and the ambient environment outside the ink reservoir.
In accordance with the present invention, the elastic bag has an interior in communication with the ambient air outside the ink reservoir having a cover body through an opening orifice mounted on the cover body of the ink reservoir so that the ambient air outside the ink reservoir freely passes in and out the elastic bag.
Preferably, the filter is mounted inside a positioning hole at a bottom of the ink reservoir.
Preferably, the positioning hole defines a blocking flange radially protruded toward a central axis of the positioning hole, a specific bore diameter and a specific mold drawing angle with a specific taper for the filter to be positioned thereinside.
Preferably, a proportion between a biggest volume of the elastic bag when expanded completely and a total volume of the ink reservoir ranges from 10% to 60%.
Preferably, the elastic bag is made of a polymer with a yield strength ranged from 5600 to 6400 kg/cm2.
Preferably, the filter is made of a material having plural fibers aligned in an axial direction.
Preferably, the filter is made of polymers of polypropylene and polythene.
Preferably, the filter has a density ranged from 0.01 to 0.8 g/cm3.
Preferably, a flowing channel between the filter and the ambient air outside the ink reservoir is provided for passing by and entering the ambient air outside the ink reservoir into the interior of the ink reservoir through the filter, and holding the ink therein temporarily.
Preferably, flowing channel has an end corresponding to the positioning hole and communicating with an aperture on a cover board covering completely the flowing channel, thereby the ambient air outside the ink reservoir passing by the aperture to the filter, and entering the interior of the ink reservoir.
Preferably, the ink reservoir has a print head using a thermal bubble system for ejecting the ink, and a printing chip mounted thereunder.
According to another aspect of the present invention, a pressure regulation apparatus for an ink reservoir having a printing chip mounted thereunder and an interior for holding an ink, comprises: an elastic bag provided in the ink reservoir and having an interior in communication with an ambient air of an ambient environment outside the ink reservoir through an opening orifice mounted on a cover body of the ink reservoir so that the ambient air outside the ink reservoir freely passes in and out the bag; and a porous filter for entering the ambient air outside the ink reservoir into the interior of the ink reservoir therethrough, thereby the elastic bag and the porous filter complementarily regulating a pressure difference between the interior of the ink reservoir and the ambient environment outside the ink reservoir.
The foregoing and other features and advantages of the present invention will be more clearly understood through the following descriptions with reference to the drawings, wherein: